The shelf life of produce or produce materials, including whole plants and parts thereof including fruits, vegetables, tubers, bulbs, cut flowers and other active respiring plants or plant materials, is typically determined, at least in part, by the amount of an ethylene hormone generated by the respiring plant material. Ethylene is a known plant ripening or maturation hormone. At any substantial concentration of ethylene in and around the plant material, the maturation of the plant is initiated, maintained or accelerated, depending on concentration. Ethylene-sensitive and—insensitive horticultural commodities (produce and ornamentals) are categorized as being climacteric or non-climacteric on the basis of the pattern of ethylene production and responsiveness to externally added ethylene. Climacteric crops respond to ethylene by an early induction of an increase in respiration and accelerated ripening in a concentration-dependent manner. Non-climacteric crops ripen without ethylene and respiration bursts. However, some non-climacteric crops are sensitive to exogenous ethylene, which can significantly reduce post harvest shelf life. Non-climacteric produce harbor several ethylene receptors which are active. Therefore, exposure of non-climacteric produce to exogenous ethylene can trigger physiological disorders shortening shelf life and quality. See, Burg et al., Plant Physiol. (1967) 42 144-152 and generally Fritz et al. U.S. Pat. No. 3,879,188. Many attempts have been made to either remove ethylene from the ambient package atmosphere surrounding the produce or to remove ethylene from the storage environment in an attempt to increase shelf life. Reduced ethylene concentration is understood to be achieved through a decrease in the stimulus of a specific ethylene receptor in plants. Many compounds other than ethylene interact with this receptor: some mimic the action of ethylene; others prevent ethylene from binding and thereby counteract its action.
Many compounds that act as an antagonist or inhibitor block the action of ethylene by binding to the ethylene binding site. These compounds may be used to counteract ethylene action. Unfortunately, they often diffuse from the binding site over a period of several hours leading to a longer term reduction in inhibition. See E. Sisler and C. Wood, Plant Growth Reg. 7, 181-191 (1988). Therefore, a problem with such compounds is that exposure must be continuous if the effect is to last for more than a few hours. Cyclopentadiene has been shown to be an effective blocking agent for ethylene binding. See E. Sister et al., Plant Growth Reg. 9, 157-164 (1990). Methods of combating the ethylene response in plants with diazocyclopentadiene and derivatives thereof are disclosed in U.S. Pat. No. 5,100,462 to Sisler et al. U.S. Pat. No. 5,518,988 to Sister et al. describes the use of cyclopropenes having a C1-4 alkyl group to block the action of ethylene.
A suitable olefinic antagonist or inhibitor of receptor sites or ethylene generation in produce is 1-methylcyclopropene, derivatives and analogs thereof have also been tried as an antagonist or inhibitor for the generation of ethylene from respiring plant or produce material. 1-methyl-cyclopropene (1-MCP), 1-butene and other olefins have been shown to have at least some measurable activity for inhibiting ethylene generation and thus extending shelf life. A number of proposals have been made for the method of producing and releasing 1-MCP to inhibit ethylene release and as a result slowing maturation and maintaining the quality of plant materials. Currently 1-MCP is dispensed by the release of 1-MCP from a moisture activated powder or sachet containing complexed 1-MCP. In these technologies, 1-MCP is released from a point source which causes a concentration gradient within the storage chamber thus resulting in a variation in maturation inhibition wherein some produce has an extended life time where other produce exposed to a lesser concentration 1-MCP tends to have less inhibition of ethylene and has a reduced shelf life.
Notwithstanding these efforts, there remains a substantial need in the art for improved plant maturation and degradation prevention. In particular, pressure from worldwide urbanization, manufacturing, and population growth necessitates development of new technologies to increase the efficiency and yield of natural resources expended on delivering food to the growing global population. In the United States, for example, it is estimated that between 8% and 16% of profit loss of fresh produce is due to spoilage and shrinkage which is estimated at $8 billion-$28 billion system wide. This loss translates to significant wasted resources, for example pesticides, fertilizer, and herbicide use; land and water use; transportation, including oil and gas use; and resources associated with the storage of produce. Loss of these and other resources are due to inefficiencies in production and delivery that allows significant spoilage of fruits and vegetables before these critical products can reach the consumer. The United Nations Asian and Pacific Centre for Agricultural Engineering and Machinery's Feasibility Study on the Application of Green Technology for Sustainable Agriculture Development states:
“Technology is a link that connects sustainability with enhanced productivity, where natural resource productivity is efficiently maintained by carefully planning the conservation and exploitation of resources such as soil, water, plants, and animals.”
(Feasibility Study on the Application of Green Technology for Sustainable Agriculture Development, United Nations Asian and Centre for Agricultural Engineering and Machinery, at p. 20.) Climate change is raising the stakes for agricultural technology as the world population grows and the amount of arable land shrinks. More mouths to feed, plus less arable land and changing rainfall patterns, means growing demand for technology that lets farmers do more with less. The European Commission recently announced an initiative to optimize food packaging without compromising safety in order to reduce food waste (Harrington, R., “Packaging placed centre stage in European food waste strategy,”). The initiative is in response to recent findings that up to 179 kg of food per person is wasted each year. The plan stresses the need for innovation, such as “active packaging” or “intelligent packaging” as one aspect of the solution.
Technology that addresses the issue of fruit and vegetable spoilage is therefore of critical importance as a “green” technology that reduces waste of food and its associated resources by increasing the effective efficiency of arable land.